There are many applications that require objects to be deployed and later retrieved from the bottom of a body of water, and of particular interest is the retrieval of fishing traps in the ocean. To facilitate retrieval, buoys and vertical fishing lines are attached to a trap or a series of traps to mark the location and provide a point of attachment to bring the trap back up to the surface and onto the deck of the vessel.
Although these buoys are visible on the surface, the lines descending from the buoys are nearly invisible to aquatic animals such as whales, dolphins, sharks, sea turtles, seals, and other large animals who swim into the lines and become tangled. Specifically, endangered Northern Atlantic right whales are continuously threatened by entanglement with fishing gear dispersed throughout their natural habitat including gear set to catch lobsters, crabs, cod, haddock, and other commercially valuable fish. Although many of these large animals are capable of breaking a sufficiently thin line from the trap, many animals still cannot remove all of the line from their fins. Others die while tangled in the line of the tethered trap. Heavier gear such as those used in the offshore fishery appears to present an even larger risk for North Atlantic right whales, because offshore traps require using lines which are far more robust than shallow water gear. Incidents of entangled animals leads to seasonal closures of fishing areas and increasingly limits the available areas for fisherman. Closures are likely to continue and may expand as government regulations increase.
Entanglement mitigation efforts are currently in effect for shallow water fishing (i.e., “inshore fishing”) which namely use weak lines and weak links/splices in the line designed to break upon sufficient force. While these methods may have reduced the problem, many animals are still negatively impacted by the use of vertical lines in fishing. Furthermore, these mitigation techniques are not viable for deeper waters (i.e., “offshore fishing”) where heavier lines are needed to withstand the water conditions and to support the retrieval of multiple traps on a single “long line” configuration.
On-call fishing gear aims to reduce the entanglements of North Atlantic right whales and other marine mammals and the number of areas otherwise closed off to trap fishing. On-call fishing, not currently used extensively in the U.S., secures vertical lines down near the water body floor until released to the surface for hauling. One on-call system is described by Fiotakis in U.S. Pat. No. 6,261,142. Unfortunately, most on-call systems require specialized deck gear and are too expensive to be commercially-viable for the average fisherman for traps and gillnet gear. These costs only increase as the gear is modified for offshore fishing, which requires heavier lines, longer lengths, and stronger equipment.
While certain on-call systems and other “rope-less” systems have been proposed to reduce animal entanglements, most if not all are used for inshore fishing with water depths of about 50 to 70 m but are incapable of withstanding water conditions over 100 m. The offshore lobster fishery has water depths up to 300 m or more, and high surface currents of about 1 to 2 knots. When used in deep waters and high currents, existing on-call gear fails to operate correctly, often being dragged from its designated location and permanently lost. Systems suitable for deep water must be designed for the high currents with compensation in weight, buoyancy, and dimension. Thus, the existing lightweight on-call technologies are only reliable at shallow depths.
Existing systems are further plagued with several other design issues which prevent deep water use. To be effective, deep water systems would require increased strength and greater overall weight; therefore, deep water systems also must be balanced for buoyancy, often requiring up to 200 lbs of positive buoyancy capable of surviving great depths. Furthermore, these existing systems typically employ weak links and reduced breaking strength ropes which are cost-effective and suitable for shallow water but are not viable for the large and heavy trawls of up to 50 traps that are used in offshore fishing.
Therefore, there is an unmet need, particularly in the fishery industry, to provide a robust on-call fishing gear system capable of use in deep water and high currents while maintaining a lower impact on the surrounding ecological environment.